JP2000077616A - Dielectric element, its manufacture, and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric element, its manufacturing method, and a semiconductor device which maintain a great residual polarization and sound functions. SOLUTION: A high dielectric thin film 32 used for a ferroelectric element is a ferroelectric containing an Ia group element, a Mg element, or a Ca element, and this high dielectric thin film 32 is pinched between an upper electrode 31 and a lower electrode 32, and formed on an underlayer substrate 34. In the high dielectric element, a high dielectric thin film is a high dielectric containing the Ia group element, the Mg element, or the Ca element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dielectric element used as a ferroelectric element such as a FeRAM or a high dielectric element such as a DRAM, a method of manufacturing the same, and a semiconductor device.

[0002]

2. Description of the Related Art A non-volatile memory, FeRAM (Fer
Roelectric Random Access Memory) uses a ferroelectric as a capacitor material. The FeRAM can retain the stored contents even when the power is turned off by utilizing the fact that the ferroelectric has two remanent polarizations having different polarities. The speed at which information is rewritten is also very fast, less than μs, and is attracting attention as an ideal next-generation memory. In order to increase the storage capacity, miniaturization of circuit components is required, and miniaturization of capacitors is being performed. In order to miniaturize the capacitor, measures such as thinning the dielectric material, using a ferroelectric substance with a larger remanent polarization, flattening the structure of the element consisting of the ferroelectric substance and the electrodes above and below it, and making them three-dimensional are necessary. is there.

Japanese Patent Application Laid-Open No. Hei 5-190797 discloses a method of using lead zirconate titanate (PZT) as a ferroelectric material to suppress the reactivity between the ferroelectric material and a metal electrode. A semiconductor memory device in which a silicon nitride film (SiNx) is formed as a diffusion preventing layer will be described.

As a semiconductor memory, a DRAM (Dynamic Random Access) characterized by high-speed rewriting of data is used.
Memory). This DRAM has entered the era of increasing the capacity of 16 Mbits and 64 Mbits with the progress of high density and high integration technology. For this reason, miniaturization of circuit components is required, and in particular, miniaturization of capacitors for storing information is being performed. Means for miniaturizing the capacitor include reducing the thickness of the dielectric material, selecting a material having a high dielectric constant, and flattening the structure formed by the upper and lower electrodes and the dielectric to make the capacitor three-dimensional. As a material having a high dielectric constant, that is, a high dielectric substance, a crystal structure of a single lattice of a perovskite structure, BST ((B
a / Sr) TiO ₃ ), which is known to have a larger dielectric constant (ε) than SiO ₂ / Si ₃ N ₄ .

[0005] In addition, in the memory using the BST, it is aimed to operate at a low voltage in accordance with high integration. For this purpose, it is necessary to increase the capacitance of the dielectric element used in the memory, and the use of a dielectric having a higher dielectric constant, an increase in the area of the electrode, and a reduction in the thickness of the high dielectric are being studied. . An example using a high dielectric is
International Electron Device Meeting Technical Digest 823 1991
(IEDM Tech. Dig.:823, 1961).

[0006] However, in the dielectric element used in the above-mentioned memory, a low dielectric constant layer or a gigantic crystal with grain growth may be formed between the electrode and the dielectric thin film. When a low dielectric constant layer is formed, the capacitance of the entire device becomes smaller,
The remanent polarization (Pr) becomes small, and does not have a function as a dielectric element. When a giant crystal is formed, a leak current flows in the grain boundary of the crystal, and the withstand voltage characteristic of the dielectric element is reduced. Therefore, a voltage sufficient for operating the dielectric element cannot be applied. In particular, when the electrode is a metal, a transition layer is formed at the interface between the dielectric thin film and the metal electrode by a diffusion reaction of elements. The transition layer has a decrease in remanent polarization (Pr),
There is a problem that the coercive electric field (Ec) increases, the film fatigue occurs, and the function as a dielectric element is reduced. An object of the present invention is to provide a dielectric element which maintains a large remanent polarization and functions satisfactorily, a method of manufacturing the same, and a semiconductor device.

[0007]

A feature of the present invention that achieves the above object is that the dielectric contains a Group Ia element, an Mg element, or a Ca element. According to this feature, since the dielectric contains the K element, the crystallization temperature of the dielectric can be lowered. Therefore, a heat treatment for crystallization can be performed at a low temperature. At this time, the dielectric can be formed without reacting the dielectric with the electrode in contact with the dielectric, and a dielectric that functions properly can be formed. A body element can be obtained. The group Ia element is preferably Li, Na, K. The dielectric preferably contains a Group Ia element, a Mg element, or a Ca element at a ratio of 0.5 part by weight or more and 10 parts by weight or less based on 100 parts by weight of the dielectric.

Further, the dielectric substance has a chemical structural formula (AO)
²⁺ (B _y-1 C _y O _{3y + 1} ) ^2- (where A is Tl, Hg, P
b, Bi, or a rare earth element, and B is Bi, Pb,
Ca, Sr, or Ba, and C is Ti, N
b, Ta, W, Mo, Fe, Co, Cr, or Zr. ) Or the chemical structural formula (P
b _1-x A _x ) (Zr _1-y Ti _y ) O ₃ (where A is La, B
a or Nb, 0 ≦ x ≦ 0.2, and 0 <y
≦ 1. With the crystal structure of (1), the dielectric is a ferroelectric, and a ferroelectric element can be obtained. This ferroelectric element is a healthy ferroelectric element that maintains a high remanent polarization Pr value, has a low coercive electric field Ec value, and has suppressed film fatigue.

Here, the chemical structural formula (AO) ²⁺ (B _y-1 C _y
O _{3y + 1} ) ^2- includes the case of (A ₂ O ₂ ) ²⁺ (B _y-1 C _y O _{3y + 1} ) ^2- . In particular, when Bi is used as the A element, (A ₂ O ₂ ) ²⁺ (B _y-1 C _y O _{3y + 1} ) ^{2- is obtained} .
= Bi, B = Sr, C = Ta, y = 2 The above chemical structural formula (BiO) ²⁺ (Sr ₁ Ta ₂ O ₇ ) ²⁻ is represented by (Bi
_{Since 2} O ₂ ) ²⁺ (Sr ₁ Ta ₂ O ₇ ) ²⁻ , SrBi ₂ T
It is equivalent to a ₂ O ₉ . When Tl and Hg are used as the A element, (AO) ²⁺ (B _y-1 C _y O _{3y + 1} ) ^2- and (A
₂ O ₂ ) ²⁺ (B _y-1 C _y O _{3y + 1} ) ^2- crystal structure, where (AO) ²⁺ (B _y-1 C _y O _{3y + 1} ) ^2- It represents both.

Further, the dielectric substance has a chemical structural formula (Ba _1-x S
With a crystal structure of (r _x ) TiO ₃ (where 0 ≦ x ≦ 1), the dielectric is a high dielectric, and a high ferroelectric element can be obtained. This high ferroelectric element has a large capacitance,
It is a highly ferroelectric element that maintains a high remanent polarization Pr value, has good withstand voltage characteristics, and functions soundly.

Another feature of the present invention is that the formation of a dielectric containing a group Ia element, a Mg element, or a Ca element is performed at a temperature of 250 ° C. or more and 500 ° C. or less. According to this feature, K
The dielectric containing the element has a low crystallization temperature,
Since film formation can be performed at a temperature of higher than or equal to 500 ° C. and lower than 500 ° C., a reaction between the dielectric and an electrode in contact with the dielectric can be suppressed. Therefore, a sound dielectric can be formed, and a dielectric element that functions soundly can be obtained.

In forming the dielectric, I
a step of providing an amorphous dielectric containing a group a element, a Mg element, or a Ca element; and a step of performing a heat treatment for crystallizing the amorphous dielectric at a temperature of 250 ° C. or more and 500 ° C. or less. Good. If the dielectric is ferroelectric, 35
At a temperature lower than 0 ° C., a group Ia element, a Mg element or C
An amorphous ferroelectric containing the element a can be provided, and heat treatment for crystallizing the amorphous ferroelectric is performed at 350 ° C. or higher and 50 ° C.
It can be performed at 0 ° C. or lower. Within these temperature ranges, the reaction between the ferroelectric and the electrode in contact with the ferroelectric can be suppressed. Therefore, a sound ferroelectric can be formed, and a sound dielectric element can be obtained.

When the dielectric is a high dielectric, the temperature is 250 ° C.
At a lower temperature, an amorphous high dielectric substance containing a Group Ia element, an Mg element, or a Ca element can be provided, and heat treatment for crystallizing the amorphous high dielectric substance is performed at 250 ° C. or higher and 450 ° C.
The following can be performed. In these temperature ranges,
The reaction between the high dielectric and the electrode in contact with the high dielectric can be suppressed. Therefore, a sound high dielectric can be formed, and a dielectric element that functions soundly can be obtained. In forming the dielectric, a step of adding a group Ia element, an Mg element, or a Ca element to the material of the dielectric may be included.

A feature of the present invention is that the semiconductor device has a dielectric element whose dielectric contains a group Ia element, Mg element or Ca element. According to this feature, since the dielectric contains the K element, the crystallization temperature of the dielectric can be lowered. Therefore, a heat treatment for crystallization can be performed at a low temperature. At this time, the dielectric can be formed without reacting the dielectric with the electrode in contact with the dielectric, and a dielectric that functions properly can be formed. A body element can be obtained. If such a dielectric element is used for a semiconductor device such as an FeRAM or a DRAM, it is possible to increase the capacity and operate at a lower voltage.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have found that the cause of the formation of a low-dielectric layer or a grain-grown giant crystal between an electrode of a dielectric element and a dielectric thin film is a high-temperature heat treatment. Was found. Conventionally, no consideration has been given to the reaction between the dielectric thin film and the electrodes provided above and below the dielectric thin film due to the high-temperature heat treatment. When forming a dielectric element, a non-crystalline dielectric thin film is crystallized by heat treatment. Conventionally, since a non-crystalline dielectric thin film was crystallized by a solid-phase reaction, a heat treatment at a high temperature of 700 ° C. or more was required. Also, when forming a dielectric thin film while crystallizing, a heat treatment at a high temperature of 700 ° C. or more was required.

However, at such a high temperature, the dielectric thin film reacts with the electrode provided in contact with the dielectric thin film, and a layer or the like which hinders the element function as described above is placed between the electrode and the dielectric thin film. Crystals are formed. The inventors have found that by adding an alkali metal or an alkaline earth metal to a dielectric, the crystallization temperature of the dielectric can be lowered, and the ferroelectric can be crystallized without reacting the ferroelectric with the electrode. Was. The principle by which the crystallization temperature of the dielectric can be lowered will be described below.

(AO) ²⁺ (B _y-1 C _y O) which is a ferroelectric substance
_{3y + 1} ) ^2- (where A is Tl, Hg, Pb, Bi, or a rare earth element, B is Bi, Pb, Ca, Sr, or Ba, and C is Ti, Nb, Ta, W, M
o, Fe, Co, Cr, or Zr. ) Or (Pb _1-x A _x ) (Zr _1-y Ti _y ) O ₃ (where A is L
a, Ba, or Nb, 0 ≦ x ≦ 0.2, and
0 <y ≦ 1. ), The addition of a Group Ia Li element, Na element, or K element facilitates the liquid phase formation between the added alkali metal and the ferroelectric. This liquid phase generation occurs at a temperature lower than the temperature of the solid phase reaction, and crystallization of the ferroelectric occurs by the liquid phase reaction. That is, the crystallization temperature of the ferroelectric is in the range of 350 ° C. or more and 500 ° C. or less. Therefore, even if the heat treatment is performed at a temperature lower than the conventional temperature of 350 ° C. or more and 500 ° C. or less, the ferroelectric can be crystallized without reacting the ferroelectric and the electrode.

Also, an alkaline earth metal Mg element, Ca
Even if an element is added to the ferroelectric, the crystallization temperature can be lowered by crystallization using a liquid phase as in the case of the group Ia. High dielectric (Ba _1-x Sr _x ) TiO
₃ (where 0 ≦ x ≦ 1), even if Li, Na, K, Mg and Ca elements are added, crystallization using a liquid phase is performed similarly to the case of ferroelectrics. By
The crystallization temperature can be lowered from 250 ° C to 450 ° C.

The Li element, the Na element, the K element, the Mg element and the Ca element may be used alone or in combination, but the total amount added is 0.5 parts by weight with respect to 100 parts by weight of the ferroelectric. The proportion is preferably at least 10 parts by weight or less. Hereinafter, a method of manufacturing a dielectric element by crystallization of a dielectric at a lower temperature than in the related art will be specifically described.

Embodiment 1 A ferroelectric device according to a first embodiment of the present invention will be described. FIG. 3 shows a schematic cross-sectional view of the ferroelectric element of this example. The ferroelectric thin film 32 used in the ferroelectric element of the present embodiment contains the K element and has a crystal structure of the chemical structural formula (BiO) ²⁺ (SrTa ₂ O ₇ ) ²⁻ . The ferroelectric thin film 32 is sandwiched between the upper electrode 31 and the lower electrode 32 and is formed on a base substrate 34. A method for manufacturing the ferroelectric element of this embodiment will be described with reference to FIG.

(1) First, a base substrate 34 is prepared. The base substrate 34 is formed by forming a 200-nm-thick TiN layer serving as a barrier layer on a Si wafer having a SiO ₂ layer on the surface. (2) The lower electrode 33 is formed on the base substrate 34. A Pt thin film having a thickness of 1000 ° is formed on the base substrate 34 by a sputtering method to form a lower electrode 33.

(3) On the lower electrode 33, a ferroelectric thin film 32 of (BiO) ²⁺ (SrTa ₂ O ₇ ) ²⁻ containing K element is formed by a sputtering method. In the sputtering method, Sr
A target obtained by adding K ₂ CO ₃ to Bi ₂ Ta ₂ O ₉ is used. The atmosphere gas was a 1: 1 mixed gas of oxygen and argon, the film formation pressure was 2 Pa, the RF power was 200 W, and the temperature of the base substrate 34 was lower than 350 ° C.
Is formed to a thickness of 250 nm. Sr in target
The proportion of Bi ₂ Ta ₂ O ₉ and K ₂ CO ₃ is 100 parts by weight of S
The ratio is such that the K element is 5 parts by weight with respect to rBi ₂ Ta ₂ O ₉ .

Since the film was formed at a temperature lower than the crystallization temperature of the undersubstrate 34, the film formed here was made of (BiO) ²⁺ (SrTa ₂ O ₇ ) ²⁻ containing K element. Dielectric thin film 3
2 is an amorphous thin film. Further, since the temperature of the base substrate 34 was lower than 350 ° C., the film could be formed without reacting with the ferroelectric thin film 32 and the base electrode 33.

(4) Next, heat treatment is performed to crystallize the amorphous ferroelectric thin film 32. Heat treatment is performed on the base substrate 3
4 is set to 50, which is the crystallization temperature of the ferroelectric thin film 32.
Raise to 0 ° C, and in air at 1 atm or oxygen
Perform for ~ 15 minutes. (5) Finally, the upper electrode 31 is formed on the crystallized ferroelectric thin film 32. A Pt thin film having a thickness of 1000 ° is formed on the ferroelectric thin film 32 by a sputtering method to form an upper electrode 31. Thus, a ferroelectric element was prepared.
In this embodiment, the heat treatment for crystallization is performed in (4), and then the upper electrode 31 is formed in (5). However, the heat treatment for crystallization may be performed after the upper electrode 31 is formed.

The ferroelectric thin film 32 after the heat treatment (4) is
As a result of EM observation, as shown in the SEM photograph of FIG. 1, the ferroelectric thin film 32 does not show a giant crystal having a grain growth, and is composed of fine ferroelectric crystals having a grain size of 100 to 1000 °. It had been. As a result of ICP analysis of the ferroelectric thin film 32, no composition indicating a transition layer or a low dielectric layer was detected, and the ferroelectric thin film 32 contained 100 parts by weight of (Bi
O) ²⁺ (SrTa ₂ O ₇ ) ^2- contained 5.0 parts by weight of element K with respect to ^2- .

FIG. 2 shows the result of examining the relationship between the voltage and the polarization of the ferroelectric element of this embodiment. 2Pr = 1 at 5V
It showed electrical characteristics of 4 μC / cm ² and Ec = 50 kV / cm. Also, the number of times of writing 10 by ± inversion of voltage 3V is 10
^It shows excellent ferroelectric properties with about 3% deterioration in properties after ¹² cycles.
No deterioration in characteristics due to the addition of elements was observed. Conventionally, since a non-crystalline dielectric thin film was crystallized by a solid-phase reaction, a heat treatment at a high temperature of 700 ° C. or more was required. However, at such a high temperature, the dielectric thin film reacts with the upper and lower electrodes to form a layer or crystal between the electrode and the dielectric thin film that hinders the function, resulting in a decrease in withstand voltage characteristics,
In some cases, the remanent polarization (Pr) was reduced, the coercive electric field (Ec) was increased, and the film was fatigued, so that it did not function as a ferroelectric element.

According to the present embodiment, the ferroelectric thin film 32 has K
The addition of the element facilitates the generation of a liquid phase between the alkali metal (K element) and the ferroelectric. This liquid phase generation occurs at a temperature lower than the temperature of the solid phase reaction, and the crystallization of the ferroelectric thin film 32 is performed by the liquid phase reaction, so that the crystallization temperature of the ferroelectric thin film 32 is lowered to 500 ° C. Therefore, since the heat treatment can be performed at a low temperature, the ferroelectric thin film 32 can be crystallized without reacting the dielectric thin film 32 with the upper and lower electrodes, and a ferroelectric element that functions properly can be obtained. Can be made.

(BiO) ²⁺ (SrTa) containing element K
FIG. 5 shows the relationship between the heat treatment temperature of the ₂ O ₇ ) ^2- ferroelectric element and the Pr characteristics. The vertical axis in FIG. 5 is a value (Pr / P) normalized by Pr at 5 V of a ferroelectric element manufactured at 500 ° C.
r (500)). As shown in FIG.
Pr / Pr (500)> 0.9 in a temperature range of 50 ° C. or more
5 showed very excellent characteristics.

100 parts by weight of (BiO) ²⁺ (SrTa ₂
When K ₂ CO ₃ is added to O ₇ ) ^{2- in} a range where the K element is 0.5 part by weight or more and 10 parts by weight or less, 2Pr at 5 V> 10 μC / cm ² , and Ec = 45 to 60 kV /
cm electrical characteristics. Li ₂ C instead of K ₂ CO ₃
Even when O ₃ , Na ₂ CO ₃ , MgCO ₃ , and CaCO ₃ are added, if the same manufacturing method as described above is performed, 2 at 5 V
Pr> 10 μC / cm ² , Ec = 45-60 kV / cm
The electrical characteristics of

FIG. 8 shows the results of a study on the relationship between the amount of addition and the crystallization temperature. The fabrication method is the same as described above ((B
iO) ²⁺ (SrTa ₂ O ₇ ) ^2- ) 100 parts by weight of K
₂ CO ₃ in the range of 0 to 15 parts by weight in terms of K element, Li ₂ C
O ₃ in the range of 0 to 15 parts by weight in terms of Li element, Na ₂ CO
₃ range from 0 to 15 parts by weight as viewed in Na elements, the range of 0 to 15 parts by weight of MgCO ₃ as viewed in Mg element, the CaCO ₃ C
It was added in the range of 0 to 15 parts by weight in view of element a. The crystallization temperature in the figure is 2 at 5 V.
It shows the minimum crystallization temperature that satisfies Pr> 10 μC / cm ² . FIG. 8 shows that the minimum crystallization temperature becomes 350 ° C. or more and 500 ° C. or less when any of the additional elements is added in the range of 0.5 part by weight or more and 10 parts by weight or less. Further, an element having a large width (tolerance) of an addition amount required to achieve a crystallization temperature of 350 ° C. is K>Na> M
g, Ca> Li.

Similarly, K ₂ CO ₃ , Li ₂ CO ₃ , Na ₂ C
O ₃ , MgCO ₃ , and CaCO ₃ are mixed to form Li, Na,
K, Mg, and Ca were added in a total amount of 0 to 15 parts by weight. FIG. 9 shows the result of examining the relationship between the amount of addition and the crystallization temperature. As is clear from FIG.
an element selected from the group consisting of a, K, Mg, Ca
In the case of adding in combination of more than one kind, the total addition amount is 0.5 parts by weight or more as in the case of the single element described above.
If it is added within a range of 0 parts by weight or less, the crystallization temperature becomes 3
The temperature can be 50 ° C or higher and 500 ° C or lower.

Embodiment 2 A ferroelectric device according to a second embodiment of the present invention will be described. The ferroelectric thin film used in the ferroelectric element of this embodiment contains the element K and has a crystal structure of the chemical structural formula Pb (Zr _0.4 Ti _0.6 ) O ₃ , and the chemical structural formula (Pb _{1 -x} A _x ) (Zr _1-y Ti _y ) O
₃ corresponds to the case where x = 0 and y = 0.6. The ferroelectric element of this embodiment is manufactured in the same manner as in the first embodiment. Pt (1000 °) / the same as in the first embodiment
Pb on TiN (200 °) / SiO ₂ / Si substrate
(Zr _0.4 Ti _0.6 ) O ₂ 100 parts by weight of K ₂ CO ₃
Was formed by a sputtering method using a target to which 5 parts by weight was added in view of K element. The sputtering gas is a 1: 1 mixed gas of oxygen and argon, the deposition pressure is 2 Pa, R
The F power was 200 W and a film thickness of 250 nm was obtained. Thereafter, heat treatment was performed at a temperature of 500 ° C. for 10 to 150 minutes in the air or oxygen at 1 atm.

Through the above operation, a ferroelectric layer Pb (Zr _0.4 Ti _0.6 ) O ₃ containing the element K was obtained. As a result of examining the relationship between the voltage and the polarization of the ferroelectric element, 2P at 5 V was obtained.
It showed electrical characteristics of r = 36 μC / cm ² and Ec = 50 kV / cm. In addition, when the number of writings was 10 ⁹ times due to ± inversion of the voltage of 3 V, the characteristics were degraded by about 10%, indicating excellent ferroelectric characteristics, and no characteristic deterioration due to the addition of the K element was observed. Pr value normalized by Pr at 5 V of the ferroelectric element manufactured at 500 ° C. (Pr / Pr (500))
Is Pr / Pr (500) in a temperature range of 350 ° C. or more>
0.95 showed very excellent characteristics.

K ₂ CO ₃ was added in the range of 0.5 to 10 parts by weight of K element with respect to 100 parts by weight of Pb (Zr _0.4 Ti _0.6 ) O ₃ , and was prepared in the same manner as described above. However, 2Pr> 30 μC / cm ^{2 at} 5 V, Ec =
Electrical characteristics of 45 to 60 kV / cm were obtained. further,
In a crystal structure consisting of the chemical structural formula (Pb _1-x A _x ) (Zr _0.4 Ti _0.6 ) O ₃ , the element A is replaced with La, Ba, and Nb elements, and the ratio of x is 0 ≦ x ≦ 0.2. A ferroelectric thin film was formed in the same manner as described above while changing the thickness within the range. In forming the ferroelectric thin film, (Pb _1-x A _x ) (Zr
_0.4 Ti _0.6 ) 5 parts by weight of K element was added as an additional element to 100 parts by weight of O ₃ . Table 1 shows 500 ° C
2Pr at 5 V of these ferroelectric devices manufactured by
Values (unit: μC / cm ² ). As shown in Table 1, the 2Pr values at 5 V of the ferroelectric devices manufactured at 500 ° C. in the same manner as above were all 30 μC / cm ^2.
The above and excellent characteristics were shown.

[0035]

[Table 1]

Further, the chemical structural formula (Pb _0.9 A _0.1 ) (Zr
_1-y Ti _y ) In the crystal structure composed of O ₃ ,
a, Ba, and Nb elements are substituted, and the ratio of y is 0 <y ≦ 1.
The ferroelectric thin film was formed in the same manner as described above except that the thickness was changed within the range of 0. In forming a ferroelectric thin film, (P
b _0.9 A _0.1 ) (Zr _{1 -y} Ti _y ) O ₃ was added in an amount of 5 parts by weight of element K to 100 parts by weight of O ₃ .
Table 2 shows 5 of these ferroelectric devices manufactured at 500 ° C.
The 2Pr value at V (unit: μC / cm ² ) is shown. As shown in Table 2, the 2Pr value greatly changes depending on the y value, and particularly high Pr in the range of 0.5 ≦ y ≦ 0.75.
Characteristics were obtained.

[0037]

[Table 2]

[Embodiment 3] A high dielectric device according to a third embodiment of the present invention will be described. FIG. 4 shows a schematic cross-sectional view of the high dielectric element of this example. The high-dielectric thin film used in the high-dielectric element of the present embodiment contains the element K and has a crystal structure represented by a chemical structural formula (Ba _0.5 Sr _0.5 TiO ₃ ). The high dielectric element of this embodiment is also manufactured in the same manner as in the first embodiment. As the base substrate 44, a Si wafer including a 200-nm-thick TiN layer barrier layer formed while heating to 300 ° C. and a SiO ₂ layer formed by thermal oxidation was used. Next, the lower electrode 43 was formed on the base substrate 44. The lower electrode 43 was formed by forming a Pt thin film at 200 ° by a sputtering method while heating the base substrate 44 to 350 ° C. In order to form the high dielectric thin film 42 on the lower electrode 43, Ba, Sr, Ti, and K elements are replaced by (Ba _0.5 Sr _0.5 ) TiO ₃ with 100 parts by weight of K ₂ CO ₃ by K element. The film was formed by a sputtering method using a target added at a ratio of 5 parts by weight. The sputtering gas was argon gas, the deposition pressure was 2 Pa, the RF power was 200 W, and a film thickness of 25 nm was obtained. Then 1at
The heat treatment was performed in air or oxygen at a temperature of 450 ° C. for 1 to 30 minutes. Through the above operation, a high dielectric layer (Ba _0.5 Sr _0.5 ) TiO ₃ containing the element K was obtained.

As a result of ICP analysis, the obtained high dielectric layer contained 5.0 parts by weight of K element with respect to 100 parts by weight of (Ba _0.5 Sr _0.5 ) TiO ₃ . Next, a Pt thin film of the upper electrode 41 was formed on the high dielectric thin film 42 by a sputtering method at room temperature at 200 ° to produce a high dielectric element. (Ba _0.5 Sr _0.5 ) TiO containing the K element
₃ the relationship between the heat treatment temperature and ε characteristics of the high dielectric element shown in FIG. The vertical axis in FIG. 6 is a value (ε / ε (450)) normalized by ε of the high dielectric element manufactured at 450 ° C. As shown in FIG. 6, ε / ε over a temperature range of 250 ° C. or higher.
(450)> 0.95, showing very excellent characteristics.

In this embodiment, (Ba _0.5 Sr _0.5 ) T
If K ₂ CO ₃ is added in a range of 0.5 part by weight or more and 10 parts by weight or less based on K element with respect to 100 parts by weight of iO ₃ ,
Electrical characteristics of ε> 250 were shown. L instead of K ₂ CO ₃
Even when i ₂ CO ₃ , Na ₂ CO ₃ , MgCO ₃ , and CaCO ₃ are added, when a film is formed in the same manner as described above, ε
> 250.

The crystal structure (Ba _{1 -x} Sr _x ) TiO ₃
In the high dielectric material of the above, also in BaTiO ₃ when x is 0, the ε value of the high dielectric element manufactured at 450 ° C. in the same manner as above is 0.5 parts by weight or more when K ₂ CO ₃ is viewed as a K element. 1
When added in a range of 0 parts by weight or less, the electric properties of ε> 400 were exhibited. In the high dielectric substance of the crystal structure (Ba _1-x Sr _x ) TiO ₃ , the ε of the high dielectric element manufactured at 450 ° C. in the same manner as described above is also used for SrTiO ₃ when x is 1.
As for the value, when K ₂ CO ₃ was added in the range of 0.5 part by weight or more and 10 parts by weight or less in terms of K element, electric characteristics of ε> 180 were exhibited.

[Embodiment 4] FIG. 7 is a schematic sectional view of a semiconductor device using a ferroelectric element according to the present invention. The fabrication method is described below. First, a diffusion layer 77 was formed on a Si wafer 75 by ion implantation and heat treatment, and then a SiO ₂ gate film 79 was formed by surface oxidation, and a gate electrode 78 was further formed thereon. After forming the SiO ₂ film 76 as an element isolation between a transistor and a capacitor, the ferroelectric element 7
3, 72, 72 were formed. Then, after forming the SiO ₂ film 74, the aluminum wiring 710 is formed, and the upper electrode 7 is formed.
1 and the diffusion layer 77. As a ferroelectric element,
The Pt electrode 71 and SrBi ₂ Ta ₂ O ₉ described in the first embodiment
By forming a structure including the thin film 72 and the Pt electrode 73, a semiconductor device including a ferroelectric memory element was obtained. The obtained semiconductor device of the ferroelectric memory element is a semiconductor device which can be detected by a change in the storage charge capacity obtained at a voltage of 3V.

Here, the Pt electrode 71, SrBi ₂ Ta ₂
Although the description has been made using the structure including the O ₉ ferroelectric thin film 72 and the Pt electrode 73, the Pt electrode, (Ba _0.5 Sr _0.5 ) TiO
A high dielectric memory element having a structure composed of a high dielectric thin film such as ₃ and a Pt electrode may be formed. The semiconductor device of the high dielectric memory element thus obtained is a semiconductor device having a voltage of 3 V and a storage capacitance of 30 fF. In addition, FeRA
For semiconductor devices such as M and DRAM, the use of the dielectric element of the present invention enables an increase in capacity and operation at a lower voltage.

In the above embodiment, the TiN layer was used as the barrier layer formed on the Si substrate.
IN, Ta, etc. may be used. In addition to Pt, W, PtTi, Ru, Ir, A
1, Cu, RuO _2, IrO _{2 and the} like can be used. In addition to the sputtering method, MOCVD performed in oxygen or excited oxygen may be used to form the dielectric film.
Method, a spin coating method using a metal alkoxide or an organic acid salt as a starting material, or a dip coating method may be appropriately selected.

[Fifth Embodiment] A non-contact type memory card 50 according to a fifth embodiment of the present invention will be described. The non-contact type memory card 50 of this embodiment shown in FIG. 11 has a data ROM 51 for storing data, a FeRAM element 52,
A contactless interface 53 and an antenna 54 are provided on the card. As the FeRAM element 52, the ferroelectric element described in the first to fourth embodiments is used. The data ROM 51, the FeRAM element 52, and the non-contact interface 53 are mutually connected by a signal line through which data flows. Non-contact interface 5
An antenna 54 is connected to the signal line 3.

Information from the outside is sent from the antenna 54 to the non-contact interface 53 and is converted into a voltage signal. With this voltage signal, the FeRAM element 52 can be driven to write information or read information from the data ROM 51. In a conventional memory card, an applied voltage of 16 V was required because a nonvolatile element such as an EEPROM element was used. In this embodiment, since the FeRAM element is used, the voltage signal can be reduced to 5 V or less.

[0047]

According to the present invention, the dielectric is a group Ia element,
By containing the Mg element or the Ca element, a heat treatment for crystallization can be performed at a low temperature, and at this time, the dielectric and the electrode in contact with the dielectric do not react with each other to form the dielectric. Thus, a dielectric element that functions properly can be obtained.

Further, the dielectric substance has a chemical structural formula (AO)
²⁺ (B _y-1 C _y O _{3y + 1} ) ^2- (where A is Tl, Hg, P
b, Bi, or a rare earth element, and B is Bi, Pb,
Ca, Sr, or Ba, and C is Ti, N
b, Ta, W, Mo, Fe, Co, Cr, or Zr. ) Or the chemical structural formula (P
b _1-x A _x ) (Zr _1-y Ti _y ) O ₃ (where A is La, B
a or Nb, 0 ≦ x ≦ 0.2, and 0 <y
≦ 1. With the crystal structure of (1), the dielectric is a ferroelectric, and a ferroelectric element can be obtained. This ferroelectric element is a healthy ferroelectric element that maintains a high remanent polarization Pr value, has a low coercive electric field Ec value, and has suppressed film fatigue.

Further, the dielectric substance has the chemical structural formula (Ba _1-x S
With a crystal structure of (r _x ) TiO ₃ (where 0 ≦ x ≦ 1), the dielectric is a high dielectric, and a high ferroelectric element can be obtained. This high ferroelectric element has a large capacitance,
It is a highly ferroelectric element that maintains a high remanent polarization Pr value, has good withstand voltage characteristics, and functions soundly.

According to another feature of the present invention, the dielectric containing K element has a low crystallization temperature and can be formed at a temperature of 250 ° C. or more and 500 ° C. or less.
Reaction between the dielectric and the electrode in contact with the dielectric can be suppressed. Therefore, a sound dielectric can be formed, and a dielectric element that functions soundly can be obtained.

When the dielectric is a ferroelectric, the temperature is 350 ° C.
At a lower temperature, an amorphous ferroelectric substance containing a Group Ia element, a Mg element, or a Ca element can be provided, and heat treatment for crystallizing the amorphous ferroelectric substance is performed at 350 ° C. or higher and 500 ° C.
The following can be performed. In these temperature ranges,
Reaction between the ferroelectric and the electrode in contact with the ferroelectric can be suppressed. Therefore, a sound ferroelectric can be formed, a high remanent polarization Pr value is maintained, and a low coercive electric field E is maintained.
It is possible to obtain a soundly functioning dielectric element having a c value and suppressing film fatigue.

When the dielectric is a high dielectric, the temperature is 250 ° C.
At a lower temperature, an amorphous high dielectric substance containing a Group Ia element, an Mg element, or a Ca element can be provided, and heat treatment for crystallizing the amorphous high dielectric substance is performed at 250 ° C. or higher and 450 ° C.
The following can be performed. In these temperature ranges,
The reaction between the high dielectric and the electrode in contact with the high dielectric can be suppressed. Accordingly, a sound high dielectric can be formed, a dielectric element having a large capacitance, maintaining a high remanent polarization Pr value, and having good withstand voltage characteristics and functioning well can be obtained.

If the semiconductor device has a dielectric element containing a group Ia element, a Mg element, or a Ca element, the heat treatment can be performed at a low temperature, so that the dielectric is in contact with the dielectric. A dielectric can be formed without reacting with the electrode, and a soundly functioning dielectric element can be obtained. If such a dielectric element is used for a semiconductor device such as an FeRAM or a DRAM, it is possible to increase the capacity and operate at a lower voltage.

[Brief description of the drawings]

FIG. 1 shows Sr produced at 450 ° C. when the amount of K added is 5 parts by weight based on 100 parts by weight of SrBi ₂ Ta ₂ O _9.
SEM photograph of Bi ₂ Ta ₂ O ₉ layer.

FIG. 2 Sr produced at 450 ° C. when the amount of K added is 5 parts by weight with respect to 100 parts by weight of SrBi ₂ Ta ₂ O ₉
FIG. 4 is a PE hysteresis diagram of a Bi ₂ Ta ₂ O ₉ layer.

FIG. 3 is a schematic sectional view showing a ferroelectric element according to the present invention.

FIG. 4 is a schematic sectional view showing a high dielectric element according to the present invention.

FIG. 5 is a diagram showing a relationship between a heat treatment temperature and a normalized Pr value.

FIG. 6 is a diagram showing a relationship between a heat treatment temperature and a normalized ε value.

FIG. 7 is a schematic cross-sectional view of a semiconductor device using the ferroelectric element of the present invention.

FIG. 8 is a graph showing the relationship between the amount of a single element added and the crystallization temperature.

FIG. 9 is a graph showing the relationship between the amount of mixed element added and the crystallization temperature.

FIG. 10 is a diagram illustrating a method of manufacturing the ferroelectric element according to the first embodiment.

FIG. 11 is a view showing a non-contact type memory card according to a fifth embodiment.

[Explanation of symbols]

31, 41, 81, 71: upper electrode 32, 72: ferroelectric thin film 42: high dielectric thin film 33, 43, 73: lower electrode 34, 44: base substrate 50: non-contact type memory card 51: data ROM 52: FeRAM element 53: non-contact interface 54: antenna 74, 76: SiO ₂ film 75: Si 77: diffusion layer 78: gate electrode 79: SiO ₂ gate film 710: aluminum wiring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuo Fujiwara 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Kazutoshi Higashiyama 7-1 Omikacho, Hitachi City, Ibaraki Prefecture No. 1 F term in Hitachi Research Laboratory, Hitachi Ltd. (reference) 5F038 AC05 AC09 AC15 AC18 DF05 EZ14 EZ17 5F083 AD21 FR02 JA12 JA14 JA15 JA38 JA40 PR22 PR33

Claims (10)

[Claims] 1. A dielectric, and a voltage applying means for applying a voltage to the dielectric.
A dielectric element, comprising: a group Ia element, an Mg element, or a Ca element. 2. The dielectric device according to claim 1, wherein said group Ia element is Li, Na, K. 3. The composition according to claim 1, wherein the dielectric is present in an amount of from 0.5 part by weight to 10 parts by weight based on 100 parts by weight of the dielectric.
2. The dielectric device according to claim 1, comprising a group Ia element, a Mg element, or a Ca element. 4. The method according to claim 1, wherein the dielectric has a chemical structural formula (AO):
²⁺ (B _y-1 C _y O _{3y + 1} ) ^2- (where A is Tl, Hg, P
b, Bi, or a rare earth element, B is Bi, Pb, Ca, Sr, or Ba, and C is Ti, Nb, Ta, W, Mo, Fe, Co, Cr,
Or Zr. 2. The dielectric element according to claim 1, wherein the dielectric element has the crystal structure of (1). 5. The method according to claim 1, wherein the dielectric has a chemical formula (Pb)
_1-x A _x ) (Zr _1-y Ti _y ) O ₃ (where A is La, B
a, or Nb, where 0 ≦ x ≦ 0.2 and 0 <y ≦ 1. 2. The dielectric element according to claim 1, wherein the dielectric element has the crystal structure of (1). 6. The dielectric material has a chemical structural formula (Ba _1-x S)
2. The dielectric element according to claim 1, wherein the dielectric element has a crystal structure of r _x ) TiO ₃ (where 0 ≦ x ≦ 1). 7. A dielectric, and 2 for applying a voltage to said dielectric
A method for manufacturing a dielectric element comprising:
A method for manufacturing a dielectric element, comprising forming a dielectric containing a group a element, a Mg element, or a Ca element at 250 ° C. or more and 500 ° C. or less. 8. A step of providing the amorphous dielectric containing the group Ia element, the Mg element, or the Ca element, and performing a heat treatment for crystallizing the amorphous dielectric.
8. The method for manufacturing a dielectric element according to claim 7, comprising a step of performing the heating at a temperature of 0 ° C. or more and 500 ° C. or less. 9. The method according to claim 9, wherein the dielectric material is a group Ia element, Mg
The method for manufacturing a dielectric element according to claim 7, further comprising a step of adding an element or a Ca element. 10. A semiconductor device having a dielectric element including a dielectric and two electrodes for applying a voltage to the dielectric, wherein the dielectric contains a group Ia element, a Mg element, or a Ca element. Characteristic semiconductor device.